1. Field of the Invention
The present invention relates to a data recording/reproducing apparatus such as a rotary head type digital audio tape recorder (hereinafter referred to as R-DAT) and the like which can perform recording/reproducing of digital signals.
2. Description of the Background Art
In some examples of the background art, there has been considered a magnetic recording/reproducing apparatus such as an R-DAT or the like which makes it possible to reproduce original data from partially lost data using an error correction technique during reproduction, by adding some error correction information (such as parity check code) to the original data, in the case of recording digital signals in high density on a magnetic recording medium. Although such an apparatus can completely correct data which has a very small lost part, it cannot reproduce original data in a case wherein a consecutive write error has caused data to be lost in a wide range, for example, in the case wherein a so-called flaw exists over a wide range on a magnetic tape.
In the case of using such a magnetic recording/reproducing apparatus as an auxiliary storage of a computer or the like, it is necessary to check recorded data after writing them, in order to detect such a situation as this. To check those data, for example, there is a method for verification wherein after finishing a write operation the magnetic tape is rewound to a position at which the recording was started and then run at the same speed as a speed during recording to reproduce the data to make a parity check. Such a method as this requires a long time for recording data due to the necessity of writing data again, in the case that some errors occur in the reproduced data due to a flaw on the recording medium and the errors cannot be corrected.
There is also a magnetic recording/reproducing apparatus which has improved its reliability of recording by means of a method in which the apparatus is provided with a separate writing head and a separate reading head, reproduces the data written on a magnetic recording medium with the reading head immediately after writing the data with the writing head, and compares them with the original data. Such a magnetic recording/reproducing apparatus as this improves reliability of recording by checking the recorded data to detect write errors through the comparison method or the like and writing the data again, if necessary.
FIG. 1 is a diagram showing a recording pattern of a magnetic tape on which data was recorded by the above-mentioned magnetic recording/reproducing apparatus. The magnetic tape 21 is run in the direction of arrow 23 and data Di (i=1,2,. . .) is recorded in a frame Fi (i=1,2,. . .) sequentially. In this case, when an error occurs in data D2 in frame F2 due to a defective portion or a flaw on the magnetic tape 21 as shown in FIG. 1 (1), the data D2 is re-recorded. Since the magnetic recording/reproducing apparatus has already performed recording up to data D6 in a frame F6 before the error of the data D2 is detected, data of an after the data D2 are recorded on and after a frame F7.
Since a tracking control for reproducing data from the magnetic tape 21 is performed on the basis of reproduced signals, some disorder occurs in the tracking control when reproducing frames F2 to F6 which have a defective portion 22 thereon. Since it takes a certain period of time for the tracking control to recover from this disorder, data in the frames to be reproduced for this period of time may not be reproduced correctly. Namely, the data D2 in the frame F7 and the like which were re-recorded on the magnetic tape 21 may not be reproduced correctly.
As shown in FIG. 1 (2), the defective portion 22 may be slightly overlapped on the frame F1. In this case, since a defective portion of the frame Fl occupies only a minute area, an error found in the error detection immediately after recording can be corrected.
In the case of reproducing data from the magnetic tape 21 multiple times, wear or the like of the surface of the recording medium may cause its recording state to be deteriorated or the defective portion in the frame F1 to be expanded, and this may make it impossible to correct an error in the data D1 in the frame F1. In this case, there is a problem that reproduction of the data D1 becomes impossible because the data D1 is not recorded in any frame other than the frame F1.